Fluid pressure operated reciprocatory motor

ABSTRACT

Structure including a body having a power cylinder, a reversing valve cylinder and a pilot valve cylinder, a power piston in the power cylinder and reversing and pilot valves axially moveable in the reversing and pilot valve cylinders respectively. The body defines an inlet port for connection to a fluid pump, and one or more outlet ports for connection to a fluid reservoir. Reciprocatory movement of the power piston is controlled by the reversing valve which in turn is controlled by the pilot valve. Operation of the pilot valve is controlled by a pair of piston operated check valves.

United States Patent [191 Von Ruden 1 Apr. 2, 1974 FLUID PRESSUREOPERATED 3,185,040 5/1965 Ligon 91/305 RECIPROCATORY MOTOR 3.540349lH1970 Pennther 91/306 Primary Examiner-Paul E. Maslousky Attorney,Agent, or Firm-Merchant, Gould, Smith & Edell [57] ABSTRACT Structureincluding a body having a power cylinder, a reversing valve cylinder anda pilot valve cylinder, 21 power piston in the power cylinder andreversing and pilot valves axially moveable in the reversing and pilotvalve cylinders respectively. The body defines an inlet port forconnection to a fluid pump, and one or more outlet ports for connectionto a fluid reservoir. Reciprocatory movement of the power piston iscontrolled by the reversing valve which in turn is controlled by thepilot valve. Operation of the pilot valve is controlled by a pair ofpiston operated check valves.

1 Claim, 1 Drawing Figure PATENTEU APR 2 I974 l FLUID PRESSURE OPERATEDRECIPROCATORY MOTOR BACKGROUND OF THE INVENTION This invention is in thenature of an improvement on reciprocatory fluid motors of the typedisclosed in U. S. Pat. No. 3,165,978, issued Jan. 19, 1965, to me andJan Boers. The motor disclosed in the patent operates verysatisfactorily, but the piston and piston rod structure thereof issomewhat difficult and expensive to produce with the accuracy required.

SUMMARY OF THE INVENTION An important object of this invention is theprovision of a fluid pressure operated reciprocatory motor havingreversing control mechanism that is more simple and inexpensive toproduce than heretofore, and which is highly efficient in operation anddurable in use. To this end I provide structure including a body havingtherein a power cylinder, and a plunger rod equipped piston axiallymoveable in the power cylinder, the plunger rod extendingoutwardlythrough a bore in the body. Reversing and pilot valve cylindersor chambers have axially moveable reversing and pilot valves or spoolsrespectively therein. Fluid passages connect the reversing and pilotvalve cylinders with fluid inlet and outlet ports, and other fluidpassages interconnect the pilot and reversing valve cylinders and powercylinder. A pair of passages connect opposite ends of the power cylindereach to a different end of the pilot valve cylinder, each of thesepassages having a check valve therein. The power piston is provided atits axially opposit e ends with portions that mechanically impartopening movements to each check valve at the end of each reciprocalmovement of the power piston, to permit movement of the pilot piston ina direction to cause reversing movement to be imparted under fluidpressure to the reversing valve. Each check valve is opened by fluidpressure responsive to mechanical opening of the other check valve, sothat fluid is discharged from one end of the pilot valve cylinderthrough the mechanically opened check valve and supplied to the oppositeend of the pilot valve cylinder through the fluid pressure opened one ofthe check valves,

DESCRIPTION OF THE DRAWING The single FIGURE of the drawing is ahydraulic diagram, some parts being shown in side elevation, and someparts being shown in section.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT Body structure,indicated generally by the numeral 1, defines a power cylinder 2, areversing valve cylinder 3, and a pilot valve cylinder 4. A power pistonis axially slideably mounted in the power cylinder 2 and is providedwith an axially projecting piston or plunger rod 6 that extends througha bore 7 in the body structure 1. Although not shown, the piston rod 6may be assumed to be adapted for connection to any suitable devicerequiring reciprocatory or oscillatory movement. Opposite ends 8 and 9of the power cylinder 2 are diametrically reduced for reception of hubportions 10 and 1 l of the piston 5, the bore 7 having a diametricallyenlarged bore portion 12 that opens into the portion 8 of the powercylinder 2 and which is adapted to loosely receive a tubular cam member13 welded or otherwise rigidly mounted on the end of the piston rod 6adjacent the hub portion 10 of the piston 5. The cam member 13 is formedto provide a frusto-conical cam surface 14 for a purpose which willhereinafter become apparent. A boss 15 projects axially outwardly of thepiston hub portion 11 and is provided with an axially outwardlyprojecting pin 16.

The body structure 1 is formed to provide a fluid inlet port 17 fromwhich a fluid passage 18 extends to the longitudinally central portionsof the reversing valve cylinder 3 and the pilot valve cylinder 4. A pairof fluid passages 19 and 20 extend from the reduced end portions 8 and 9respectively of the power cylinder 2 to the reversing valve cylinder 3in spaced relationship to the inlet passage 18 and at opposite sides ofthe inlet passage 18. In like manner, a pair of fluid passages 21 and 22extend from opposite end portions of the reversing valve cylinder 3 tothe longitudinally central portion of the pilot valve cylinder 4 inspaced relation to diametrically opposite sides of the inlet passage 18longitudinally of the pilot valve cylinder 4. A pair of outlet passages23 and 24 communicate with the reversing valve cylinder 3 and withoutlet ports 25. The passage 23 is disposed to communicate with thecylinder 3 between the adjacent ends of the fluid passages 19 and 21,the passage 24 communicating with the cylinder 3 intermediate theadjacent ends of the fluid passages 20v and 22. Likewise, a pair ofoutlet passages 26 and 27 extend from the pilot valve cylinder 4 tooutlet ports 28, the passage 26 communicating with the cylinder 4 inspaced relation to the adjacent end of the passage 21 and the adjacentend of the cylinder 4, the passage 27 communicating with the cylinder 24in spaced relation to the adjacent end of the passage 22 and theadjacent end of the cylinder 4. Although not shown, it may be assumedthat the outlet ports and 28 maybe a single outlet port adapted forconnection to a fluid reservoir not shown, a plurality of outlet ports25 and 28 being shown for the purpose of convenience.

A spool-like reversing valve 29 is mounted in the reversing valvecylinder 3 for axial sliding movements therein, and comprises a centralvalve piston 30 of relatively short axial length and a pair ofcooperating valve pistons 31 and 32 of relatively long axial lengthadjacent opposite ends of the valve 29. The valve pistons 31 and 32cooperate with the central valve piston 30 to define the opposite endsof respective grooves 33 and 34 each having an axial lengthsubstantially equal to the axial length of one of the valve pistons 31and 32. At its opposite ends, the reversing valve 29 is formed toprovide axial bosses 35 that are adapted to engage adjacent ends of thecylinder 3 to limit axial movement of the reversing valve 29 in oppositedirections. The piston 30 is formed to provide acentral annular groove30a.

An elongated spool-like pilot valve, indicated generally at 36, isdisposed for axial sliding movements in the pilot valve cylinder 4, andcomprises a central piston 37 of relatively short axial length, a pairof axially relatively long pistons 38 and 39, and end bosses at theopposite ends of the valve 36 and adapted to engage adjacent end wallsof the pilot valve cylinder 4 to limit axial movement of the valve 36 inopposite directions. The valve 36 is similar to the valve 29, exceptthat the piston 37 is devoid of a central annular groove like the groove30a of piston 30. The pistons 37 and 38 define opposite ends of acircumferential channel 41, the pistons 37 and 39 defining opposite endwalls of a circumferential channel 42. It should here be noted that thecentral pistons 30 and 37 of both valves 29 and 36 have an axial lengthslightly greater than the width or diameter of the inlet passage 18, thepistons 30 and 37 being disposed to pass over the inlet passage 38during axial movements in their respective cylinders 3 and 4. Theannular groove 30a insures continuous flow of fluid through the passage18 during movement of the piston 30 over the passage 18.

The body structure 1 is formed to provide a pair of fluid passages 43and 44 that extend from opposite ends of the pilot valve cylinder 4 eachtoward an opposite end of the power cylinder 2. Preferably, and asshown, the passage 43 extends from the end of the pilot valve cylinder 4adjacent the valve piston 39 toward the enlarged bore portion 12 of thepower cylinder 2, the

passage 44 extending from the pilot valve cylinder 4 adjacent the valvepiston 38 toward the diametrically reduced portion 9 of the powercylinder 2. A check valve 45 is interposed in the fluid passage 43 andcomprises a casing 46, a ball valve element 47, and a coil compressionspring 48 that yieldingly urges the ball valve element 47 into seatingengagement with a valve seat portion 49. As shown, a passage portion 50extends from the valve seat 49 to the enlarged bore portion 12, andcontains a valve actuator 51 having a portion projecting radiallyinwardly into rolling or sliding engagement with the piston rod 6 Withinthe enlarged bore portion 12.

A second check valve 52 is interposed between the end portion 9 of thepower cylinder 2 and the adjacent end of the fluid passage 44, andcomprises a valve body 53 defining a valve seat 54 from which extends apassage portion 55 to the interior of the power cylinder 2 in axialalignment with the pin 16 on the piston 5. A valve ball element 56 isurged into seating engagement with valve seat 54 by a coil compressionspring 57 that has abutting engagement with a screw plug 58 that isscrew threaded into the body structure 1 to form an abuttment for thespring 57 and to secure the valve housing 53 in the body structure 1. Across-passage 59 in the valve housing 53 provides communication betweenthe fluid passage 54 and the passage portion 55 when the valve ballelement 56 is in an open position.

OPERATION For imparting reciprocatory movement to the piston and pistonrod 6, it is assumed that the inlet port 17 is in communication with thedischarge of a source of fluid pressure, such as a pump, not shown, andthat the outlet ports 25 and 28 are connected to a fluid reservoir, alsonot shown, from which the pump receives fluid. With the pilot valve 36and reversing valve 29 positioned as shown in the drawing, fluid underpressure moves through the inlet passage 18, groove 34, and throughfluid passage to the end portion 9 of the power cylinder 2 to move thepiston 5 and piston 6 in a direction from the right to the left withrespect to the drawing, and as shown by the arrow on the piston rod 6.Fluid under pressure is also contained within the upper portion of thepassage 18, circumferential groove 42, fluid passage 22 and theright-hand end of the reversing valve cylinder 3 to hold the reversingvalve 29 in its position shown. Fluid is contained under pressure in thefluid passage 44 and the end of the pilot valve cylinder 4 adjacent thepilot valve piston 38. However, fluid in the opposite end of the pilotvalve cylinder 4 and in the passage 43 is prevented from discharge bythe check valve 45, so that the pilot valve 36 is hydraulically lockedin place.

As the piston 5 approaches the end of its movement toward the left withrespect to the drawing, the frustoconical cam portion 14 of the cammember 13 engages the adjacent end of the actuator 51 and moves the sameradially outwardly to move the valve ball member 47 to a valve openposition away from seating engagement with the valve seat 49. At thesame time, the check valve 52 is opened due to pressure of fluid in theadjacent end 9 of the power cylinder 2 so that fluid under pressuremoves the pilot valve 36 toward the opposite end of the pilot valvecylinder 4. During this movement of the pilot valve 36, fluid in theopposite end of the cylinder 4. and in the passage 43 moves axiallyinwardly of the enlarged bore portion 12, and through the fluid passage19, circumferential groove 33 in the reversing valve 29, and passage 23to the adjacent outlet port 25. As the pilot valve 36 moves to theright, the piston 37 crosses the adjacent end of the inlet passage 18and, when the pilot valve 36 is moved to its limit of movement to theright with respect to the drawing, the piston 37 is disposed so that thecircumferential groove 42 is in register with the adjacent ends of thepassages 22 and 27, the circumferential groove 41 being in register withthe adjacent ends of the inlet passage 28 and fluid passage 21. Fluidunder pressure then flows through the passage 18, circumferential groove41, and fluid passage 21 to the end of the reversing valve cylinder 3adjacent the piston 31 of the reversing valve 29. The opposite end ofthe reversing valve chamber 3 being exposed to the outlet passage 27,fluid under pressure will move the reversing valve 29 to the right withrespect to the drawing until the center piston 30 moves across the inletpassage 18, the piston 31 closing off the outlet passage 23, and thecircumferential groove 33 coming into register with the inlet passage 18and fluid passage 19. At the same time, the circumferential groove 34moves into register with the adjacent ends of the fluid passage 20 andoutlet passage 24 so that the right end power cylinderportion 9 is incommunication with the reservoir not shown. Fluid under pressure, movingthrough the fluid passage 19 into the power cylinder portion 8 impartsmovement to the power piston 5 and piston rod 6 toward the right withrespect to the drawing. In view of the fact that the fluid passage 20 isin communication with the outlet passage 24, so that a minimum fluidpressure exists in the adjacent end of the power cylinder 2, the checkvalve 52 closes to establish a fluid lock in the passage 44 to preventmovement of the pilot valve 36 in the opposite direction until the valveball element 56 is unseated by engagement with the pin 16. As soon asthe valve ball element 56 is unseated, fluid under pressure in theopposite end portion of the power cylinder 2 will move through the checkvalve 45 to move the pilot valve 36 toward the opposite end of the pilotvalve cylinder 4 to cause reversal of the reversing valve 29 and reversemovement to be imparted to the power piston 5 and piston rod 6.

With the above arrangement, there is no deadcenter relationship of anyof the moving parts, and the motor can be stopped and restarted with thepiston 5 in any position longitudinally of the power cylinder 2.Further, pressure of the check valve springs 48 and 57 is not critical,it being only necessary that these be strong enough to close theirrespective valve ball elements against pressure of fluid being movedtoward the, outlet ports 25.

If it is desired that the above-described motor utilize a piston rod atboth ends of the power piston 5, it is only necessary that the oppositeend of the body structure 1 be provided with a bore and counter-boresimilar to the bore 7 and enlarged bore portion 12, and to that a secondcheck valve 45 be substituted for the check valve 52 at the lower endportion of the passage 44. The second piston rod would of course beprovided with a valve actuator engaging cam member similar to the cammember 13.

While l have shown a preferred embodiment of my fluid pressure operatedreciprocatory motor, and briefly described a modified arrangement, itwill be understood that the same is capable of further modificationwithout departure from the spirit and scope of the invention, as definedin the claims.

What is claimed is:

1. In a fluid pressure operated reciprocatory motor:

c. said structure having inlet port means for connection to a source offluid under pressure, outlet port means, and passage means connectingsaid inlet and outlet port means to said valve cylinders and connectingsaid reversing valve cylinder to said power cylinder;

d. a pilot valve and a reversing valve axially movable in respectiveones of said valve cylinders;

e. said pilot valve having axially spaced valve pistons and interveningcircumferential grooves for controlling flow of fluid to and from saidreversing valve cylinder;

f. said reversing valve having axially spaced valve pistons andintervening circumferential grooves for controlling flow of fluid to andfrom said power cylinder and to said pilot valve cylinder;

g. said structure further having a pair of fluid passages each extendingand communicating with a different chamber of said power cylinder to adifferent end of said pilot cylinder, said fluid passages being disposedto maintain a pressure balance at opposite ends of said pilot valvecylinder during movement of said power piston between opposite ends ofsaid power cylinder;

h. a pair of check valves one each connecting one of said fluid passagesto the adjacent end of said power cylinder, each of said check valvesincluding a valve element movable between valve open and closedpositions, one of said valve elements being movable generally radiallyrelative to said piston receiving bore, the other of said valve elementsmoving axially of said power cylinder;

. said bore having a diametrically enlarged portion opening into saidpower cylinder;

j. a check valve actuator having a portion projecting into said enlargedbore portion and engaging said generally radially moving valve element;

k. a cam at one end of said piston for engagement with said check valveactuator to move its respective valve element in a valveopeningdirection;

l. and a pin projecting axially from the other end of said piston forengagement with said axially moving valve element to move the same in avalve opening direction.

1. In a fluid pressure operated reciprocatory motor: a. structureincluding Body means defining a power cylinder, a reversing valvecylinder, a pilot valve cylinder, and an axial piston rod receiving boreat one end of said power cylinder; b. a power piston axially movable insaid power cylinder and having a piston rod in said bore axially movablewith said piston; a chamber on each side of said power piston; c. saidstructure having inlet port means for connection to a source of fluidunder pressure, outlet port means, and passage means connecting saidinlet and outlet port means to said valve cylinders and connecting saidreversing valve cylinder to said power cylinder; d. a pilot valve and areversing valve axially movable in respective ones of said valvecylinders; e. said pilot valve having axially spaced valve pistons andintervening circumferential grooves for controlling flow of fluid to andfrom said reversing valve cylinder; f. said reversing valve havingaxially spaced valve pistons and intervening circumferential grooves forcontrolling flow of fluid to and from said power cylinder and to saidpilot valve cylinder; g. said structure further having a pair of fluidpassages each extending and communicating with a different chamber ofsaid power cylinder to a different end of said pilot cylinder, saidfluid passages being disposed to maintain a pressure balance at oppositeends of said pilot valve cylinder during movement of said power pistonbetween opposite ends of said power cylinder; h. a pair of check valvesone each connecting one of said fluid passages to the adjacent end ofsaid power cylinder, each of said check valves including a valve elementmovable between valve open and closed positions, one of said valveelements being movable generally radially relative to said pistonreceiving bore, the other of said valve elements moving axially of saidpower cylinder; i. said bore having a diametrically enlarged portionopening into said power cylinder; j. a check valve actuator having aportion projecting into said enlarged bore portion and engaging saidgenerally radially moving valve element; k. a cam at one end of saidpiston for engagement with said check valve actuator to move itsrespective valve element in a valve opening direction; l. and a pinprojecting axially from the other end of said piston for engagement withsaid axially moving valve element to move the same in a valve openingdirection.